Apparatus for coating surfaces and curing the same at high speeds

ABSTRACT

A machine for galvanizing and coating of steel tubing operating continuously to achieve high rates of production is provided with means for applying a protective film to a tube formed from strip steel and coated with zinc and includes means for removing the solvent from the film material and curing the material after the coating has been applied. The means includes a multistage heating apparatus to sequentially remove the solvent and cure the material.

United States Patent [151 3,667,095

Ostrowski et a]. 51 June 6, 1972 541 APPARATUS FOR COATING SURFAC3,068,119 12/1962 GOISCh ..1 18/642 x 3,122,114 2/1964 Kringel et al.....29/33 D AND CURING THE SAME A HIGH 3,322,099 5/1967 Valle ..1 18/642SPEEDS 3,338,738 8/1967 Lindemann ..1 18/642 x [72] Inventors: P gzxmade Primary Examiner-Andrew R. .luhasz Bash lcago o AssistantExaminer-Z. R. Bilinsky 731 Assignee: Allied Tube & Conduit Corporation,Har- Attorney-949091189", Hersh& Scott vey, Ill.

[57] ABSTRACT F'led: Dec. 17 1969 [22] A machine for galvanizing andcoating of steel tubing operat- [21] Appl. No.: 885,824 ing continuouslyto achieve high rates of production is provided with means for applyinga protective film to a tube formed from strip steel and coated with zincand includes [52] U.S.Cl. ..29/33D, 118/643 means for removing theSolvem from he film material and R 323k 31/02 curing the material afterthe coating has been applied. 'lhe [58} Field of Search ----2 D; 1 2means includes a multistage heating apparatus to sequentially remove thesolvent and cure the material.

ed References 5 Clains, 4 Drawing Figures UNITED STATES PATENTS3,524,245 8/1970 Searing ..29/33 D ALVANIZIUG 2 Ana Coon/v6 j 4 SIZINGnrma 1 PA! REMOVAL cumua CUT OFF COOLING J PATENTEDJHH 61972 3, 66 7.095

Fin. 1 u Q6 m VAN/ZINE 2 AND C001 1N6 O so: VENT T SIZING PAINTING IREMWAL CURING CUT OFF COOLING 4 FIG, 2

/ N VEN TOR w ar E Osirgwsg' 1 1 We ma s APPARATUS FOR COATING SURFACESAND CURING Tim SAME AT HIGH SPEEDS BACKGROUND OF THE INVENTION Thisinvention relates to a machine for continuously forming and galvanizingtubing and other shapes of endless strips of steel. More particularly,it relates to improvements in such machines which apply a protectivecoating to the tubing in a continuous manner.

The patent to Krengel et al. U.S. Pat. No. 3,122,114 discloses a machinefor Continuous Tube Forming and Galvanizing. The machine discloses inthat patent is capable of producing large quantifies of galvanizedtubing at relatively high rates of production with the advantage ofachieving great economy. Whereas much of the tubing produced by amachine of the type shown in this patent has a market when the outersurface is galv or coated with zinc, there is a need for tubing whichnot only has such a coating, but in addition, has another coating orprotective film. Such an additional coating has the advantage ofprotecting the tubing from weathering, protecting the zinc fromtarnishing and generally protecting the tubing from harrniulenvironmental situations such as are found in various atmospheres towhich the tubing might be exposed. In addition, there is a need fortubing to which coatings have been applied over the zinc for appearancepurposes; for instance, to provide colored tubing for use in furnitureand other consumer products.

l-leretofore such coatings or protective films have been applied togalvanized tubing using hand or other discontinuous methods after thetubing has been cut into desired lengths. These methods are, of course,relatively expensive and fail to achieve all the advantages to be gainedfrom methods and machines capable of continuously forming andgalvanizing the tubing.

Therefore, it is an object of this invention to provide a novel machinefor the continuous forming, galvanizing and coating of tubing.

It is another object of this invention to provide a novel machine forforming, coating and galvanizing tubing which is capable of relativelyhigh rates of production.

The invention achieves these and other objects by providing an improvedtube forming and galvanizing machine which includes means forcontinuously apply a protective film or coating to the galvanized tubingand also continuously dries and cures the coating so applied.

BRIEF DESCRIPTION OF THE FIGURES The subject matter which is regarded asthe invention is particularly pointed out and distinctly claimed in aconcluding portion of this specification. An embodiment of the inventionboth as to its structure and manner of operation together with furtherobjects and advantages thereof may be best understood by reference tothe following description taken in connection with the accompanyingdrawing in which:

FIG. 1 is a schematic illustration of a drying and curing means inaccordance with the invention;

FIG. 2 is a diagrammatic illustration of a portion of a continuousforming, galvanizing and coating machine in accordance with theinvention;

FIG. 3 is an end view of heating means and coated tubing in accordancewith the invention; and

FIG. 4 is a diagrammatic illustration of an alternative embodiment of adrying and curing means in accordance with the invention.

DETAILED DESCRIPTION Referring first to FIG. 2, there is illustrated indiagrammatic form that portion of a machine for continuously forming,galvanizing and coating tubing at high speeds with which thisapplication is particularly concerned. While this application disclosesembodiments of the invention in which the product of the machine istubing, it should be understood that the inventions utility is notlimited to the production of cylindrical tubing but that it may also beuseful in continuous machines for forming, galvanizing and coating othershapes such as tubing of various cross-sectional configurations androlled or partially rolled forms of any number of shapes such as shapedstrip or profiled strip. The structure and operation of a machine forcontinuously forming and galvanizing tubing forming a part of thisinvention is disclosed in the patent to Krengel et al. U.S. Pat. No.3,122,114 which disclosure is hereby incorporated into this applicationby reference, particularly, those portions of the disclosure of thatpatent which show and describe a continuous tube forming and galvanizingmachine up to tube sizing rolls designated by reference numeral 192 inthat patent.

It may be seen in FIG. 2 tubing 1 which has been formed from strip steeland welded and then galvanized passes from a cooling stage to the tubesizing rolls which are represented by the block 2 in FIG. 2. Theapparatus represented by this block reduces the diameter of the formedtubing to a desired size by the action of the rolls. The tubing thenpasses through an in line painting apparatus 4. The apparatus 4 may takeany one of a number of conventional forms such as spraying using air,airless or electrostatic methods, etc. The paint, coating or protectivefilm 5 to be applied by this apparatus should have the quality ofresisting weathering and protecting the zinc from tarnishing due toadverse environmental or atmospheric elements and additionally may beused for decorative purposes. In addition, it should have the quality ofadhering strongly to the surface of the galvanized tubing even when thetubing is subsequently bent into desired shapes by the users thereof.That is to say, it should have the quality of being flexible so as to bebent without cracking or breaking away from the surface of the tubing.It has been found that films made from thermosetting acrylic and siliconcopolymer resins have these desired qualities and such films may beapplied as the protective film to the tubing either with or withoutpigmenting or coloring agents.

Since such films include solvents to facilitate their application to asurface and since they are thermosetting films, it is necessary in orderto complete the coating operation to remove the solvents and cure thefilm. To this end, the invention provides an in line multistage heatingapparatus 6 downstream in the machine of the painting apparatus 4. Theapparatus 6 includes a first stage 8 producing heat sufficient to raisethe temperature of the coated tube to a value sufficient to remove thesolvents. A second in line heating stage 10 is spaced downstream of thestage 8 a distance sufficient to allow time for the solvents to leavethe coating. This stage has a heat capacity sufficient to raise thetemperature of the coated tubing to a second and higher range in orderto effect the curing of the resin material.

In one embodiment of the invention where the machine is being operatedto produce tubing continuously at the rate of -450 ft. per minute, ithas been found that if the heat applied by heating stage 8 is sufficientto raise the temperature of the coated tubing to a range of 150 to 300F., the solvent contained in the coating material will be removed. Atthe same time the heat supplied by the heating stage 10 should besufficient to raise the temperature of the coated tubing to a range of400 to 700 F. in order to efiect curing of this material.

In one embodiment of the invention where the coating being applied has athickness in excess of approximately 0.3 mils it is important that thetwo stage heating apparatus 6 be provided. If it is attempted to raisethe temperature of the coated tubing rapidly in an effort to elfect adrying and curing in one operation, it will be found that the coatingwill blister as the solvents and possible by products of a chemicalreaction will rapidly boil off and cause this phenomenon to occur.Because the rapid boiling of solvents may occur in any coating whichcontains a solvent and blistering is undesirable, another use for theinvention may be its application to machines which are coatinggalvanized strips or shapes with such materials. In this case, themultistage heating apparatus would be used to effect solvent removal inits various stages at a controlled rate of temperature increase to avoidrapid boiling.

After curing by the heating stage 10, the tubing may be passed to acooling stage 12. It should be understood that whereas for conveniencethis is illustrated in the drawing as being below the stage previouslydescribed in the actual machine it is in line with all of the otherelements of the machine in order to achieve the continuous high speedoperation desired.- The cooling stage may be constituted by one or morenozzle'rings or series of nozzles encompassing the tubing and sprayingwater thereon. Alternating the cooling could be accomplished by passingthe tubing through a water immersion bath. Likewise, in line with theremaining elements of the machine is a cut ofiapparatus 14 in the samemanner as that described in US. Pat. No. 3,256,592.

. FIG. 1 illustrates a first embodiment of the multistage heating means6. This means is constituted by a protective housing 16 having openings18 and 20 at each end thereof and supported in any suitable manner inthe machine. The openings 18 and 20 are in line with the rest of themachine and the axis of the tubing 1 being fabricated so that the tubingwill enter through the opening 18 and leave the housing 16 through theopening 20. Disposed inside of the housing is an induction heating coilconstituting the first heating means 8 for effecting solvent removal.The heating coil encompasses the tubing and is connected to a suitablesource of alternated current (not shown) to achieve the desiredinduction heating effect. As is conventional with such coils, they areformed as hollow elements and cooling water is circulated through them.Spaced along the" length of the tubing inside the housing 16 anddownstream of the first heating means 8 is the second heating means foreffecting the curing of the protective film or coating. This too isconstituted by an induction heating coil encompassing the tubing andconnected to a suitable source of electrical energy (not shown) andprovided with cooling water. The housing 16 has connected thereto, byvirtue of an opening provided in its wall, an exhaust vent 22 forproviding an exit for the evaporated solvents removed from the coatingmaterial. It is desirable to have a suitable fan or other mechanicalsuction apparatus in the exhaust vent to draw off the evaporatedsolvents and additional openings may be provided in the housing toprovide for the entry of air.

In the event it is desired to coat the tubing with a film greater than0.3 mils, the alternative embodiment of the drying and curing stage 6shown in FIG. 4 may be used. This embodiment comprises the first heatingstage 8 in order to effect solvent removal and spaced downstream alongthe length of the tubing from the heating stage 8 is a second heatingstage 10 comprising a pair of induction heating coils 24 and 26encompassing the tube. These coils can be connected in electrical serieswith each other and/or to a separate suitable source of electricalenergy.

FIG. 4 also illustrates an alternative embodiment of a housing for theheating coils. In this embodiment the housing is constituted by a boxlike lower portion 28 having upstanding end walls 30 and 32 in whichopenings 34 and 36, respectively, are provided. As before, theseopenings and the housing are in line with the remainder of the machinein order that continuous high speed operation may be achieved. A hood 38overlies the open tube of the bottom member 28 and is provided with anexhaust vent 40 for removal of the evaporated solvents. The coils 8, 24and 26 may be supported by any suitable means representeddiagrammatically in this drawing by the parts designated with referencenumerals 42, 44 and 46.

Although in accordance with the provisions of the patent statutes, thisinvention is described as embodied in various forms and the principlehas been explained together with the best mode in which it is nowcontemplatedapplying that principle, it will be understood that theapparatus shown and described is merely illustrative and the inventionis not limited thereto since alterations and modifications will readilysuggest themselves to persons skilled in the art without departing fromthe true spirit of the invention or from the scope of the annexedclaims.

What is claimed as new and desired to Patent of the United States is:

1. In a machine for the continuous forming, galvanizing and coating oftubing including means for continuously feeding an endless strip ofsteel to the machine, means forming the strip into rounded shape tobring the lateral edges together, welding means for joining the freeedges of the strip steel in a continuous seam to form' completelyenclosed lengths of tubing, means for applying molten zinc onto thesurface of the formed tubing and means for coating the tubing intopredetermined lengths, the improvement comprising means for applying athermosetting protective film on the outer surface of the formed tubing,and first heating means comprising an induction heating coilencompassing said formed tubing having a capacity sufficient to raisethe temperature of the formed tubing and the protective film to a rangeof l50to 350 F, for dry ing the protective film mounted in the machinedownstream of said protective film applying means and second heatingmeans comprising an induction heating means having a capacity sufficientto raise the temperature of the formed tubing and the protective film toa range of 400 to 700 F. for curing the protective film mounteddownstream of said first heating means.

2. In the machine of claim 1 wherein said induction heating meanscomprising said second heating means comprises a single inductionheating coil encompassing said formed tubing.

3. In the machine of claim 2 wherein the improvement further comprisesan elongated housing having its longitudinal axis in line with the axisof the formed tubing and having openings at each end thereof throughwhich said formed tubing may pass; said first and second heating meansbeing mounted in said housing; and exhaust means having a connection tothe interior of said housing for drawing off solvents evaporated fromthe protective film as a result drying it.

4. In the machine of claim 1 wherein said induction heating meanscomprising said second heating means comprises a pair of inductionheating coils spaced axially along the length of formed tubing andconnected in series with each other.

secure by Letters 5. In the machine of claim 4 wherein theimprovementfurther comprises an elongated housing having itslongitudinal axis in line with the axis of the formed tubing and havingopenings at each end thereof through which said formed tubing may pass;said first and second heating means being mounted in said housing; andexhaust means having a connection to the interior of said housing fordrawing off solvents evaporated from the protective film as a resultdrying it.

2. In the machine of claim 1 wherein said induction heating meanscomprising said second heating means comprises a single inductionheating coil encompassing said formed tubing.
 3. In the machine of claim2 wherein the improvement further comprises an elongated housing havingits longitudinal axis in line with the axis of the formed tubing andhaving openings at each end thereof through which said formed tubing maypass; said first and second heating means being mounted in said housing;and exhaust means having a connection to the interior of said housingfor drawing off solvents evaporated from the protective film as a resultdrying it.
 4. In the machine of claim 1 wherein said induction heatingmeans comprising said second heating means comprises a pair of inductionheating coils spaced axially along the length of formed tubing andconnected in series with each other.
 5. In the machine of claim 4wherein the improvement further comprises an elongated housing havingits longitudinal axis in line with the axis of the formed tubing andhAving openings at each end thereof through which said formed tubing maypass; said first and second heating means being mounted in said housing;and exhaust means having a connection to the interior of said housingfor drawing off solvents evaporated from the protective film as a resultdrying it.